Disclosed are a self-adaptive baud rate system and method. The method includes: a) receiving first data and second data; b) judging whether or not a falling edge of a start bit in a synchronization code of the first data and second data is detected; c) if the falling edge is not detected, then return to step b); and if the falling edge is detected, then a first counting is started from a rising edge after the start bit based on a reference clock, and stopped at the next falling edge, and a first count value is obtained; and a second counting is started from the falling edge where the first counting was stopped, and stopped at the next rising edge, and a second count value is obtained; and d) acquiring a baud rate according to the relationships among the first count value and the second count value and a first threshold. By way of using a CPLD to detect the baud rate and encoding format of a Modbus data frame remotely according to the present application, there is no need to manually set the baud rate and encoding format locally. The function of remote auto-detection of the baud rate and encoding format can be achieved by the present application, and the materials and assembly costs of the rotary encoder are omitted.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A self-adaptive baud rate method, comprising the steps of: a) receiving first data and second data; b) determining whether or not a falling edge of a start bit in a synchronization code of the first data and second data is detected; c) if the falling edge is not detected, returning to step b); if the falling edge is detected, starting a first counting from a rising edge following the start bit based on a reference clock, stopping the first counting at a next falling edge, and obtaining a first count value; starting a second counting from the falling edge where the first counting was stopped, and stopping the second counting at a next rising edge, and obtaining a second count value; and d) obtaining a baud rate according to the relation between the first count value and the second count value and a first threshold.
2. The self-adaptive baud rate method according to claim 1 , further comprising the step of: obtaining an encoding mode according to the relation between the first count value and the second count value and a second threshold.
3. The self-adaptive baud rate method according to claim 1 , wherein the baud rate is obtained by comparing the relation between a sum of the first count value and the second count value and the second threshold value according to an already-known baud rate correspondence table.
4. The self-adaptive baud rate method according to claim 3 , wherein the encoding mode is obtained by comparing the relation between a difference of the first count value and the second count value and the second threshold value according to an already-known encoding mode correspondence table.
5. The self-adaptive baud rate method according to claim 4 , further comprising the step of: f) determining whether a falling edge of an actual data start bit of the first data and the second data is detected; if the falling edge is not detected, returning to step f); if the falling edge is detected, starting a third counting based on the reference clock; meanwhile, outputting a first enable signal if the falling edge is from the first data, and outputting a second enable signal if the falling edge is from the second data.
6. The self-adaptive baud rate method according to claim 5 , further comprising the step of: g) forbidding the first enable signal and the second enable signal, after the third count value reaches a third threshold value.
7. The self-adaptive baud rate method according to claim 6 , wherein the first enable signal controls a first transceiver that receives the first data from a first network; and the second enable signal controls a second transceiver that the second data from a second network.
8. The self-adaptive baud rate method according to claim 7 , wherein the first threshold value is a ratio of a different baud rate to the basic clock signal; the second threshold value is a preset value to which a different specific encoding mode corresponds; and the third threshold value is the ratio of a character time corresponding to the baud rate and encoding mode derived by the baud rate detection unit to the basic clock.
9. A self-adaptive baud rate system, comprising: a first digital filter configured to receive first data from a first transceiver; a second digital filter configured to receive second data from a second transceiver; a frequency divider configured to output a reference clock to a first counter and a second counter according to an external crystal oscillator; the first counter configured to count the first data and the second data based on the reference clock, and obtain a first count value and a second count value; a baud rate detection unit configured to receive the first data and the second data from the first digital filter and the second digital filter, when detecting a falling edge of a start bit in a synchronization code of the first data and the second data, control the first counter to start a first counting from a rising edge following the start bit and stop the first counting at a next falling edge and obtain the first count value; control the first counter to start a second counting from the falling edge where the first counting was stopped until a next rising edge, and obtain the second count value; and obtain a baud rate according to the relation between the first count value and the second count value and a first threshold; the second counter configured to perform a third counting on the first data and the second data based on the reference clock, and obtain a third count value; a baud rate generator configured to control an output control unit and the second counter according to the baud rate and the encoding format detected by the baud rate detection unit together with the first data and second data; the output control unit configured to output a first enable signal or a second enable signal under the control of the second counter and the baud rate generator.
10. The self-adaptive baud rate system according to claim 9 , wherein the baud rate detection unit obtains an encoding mode according to the relation between the first count value and second count value and a second threshold.
11. The self-adaptive baud rate system according to claim 9 , wherein the baud rate detection unit obtains the baud rate by comparing the relation between a sum of the first count value and the second count value and the second threshold value according to an already-known baud rate correspondence table.
12. The self-adaptive baud rate system according to claim 11 , wherein the baud rate detection unit obtains the encoding mode by comparing the relation between a difference of the first count value and the second count value and the second threshold value according to an already-known encoding mode correspondence table.
13. The self-adaptive baud rate system according to claim 12 , wherein the baud rate generator determines whether a falling edge of an actual data start bit of the first data and the second data is detected, controls the second counter to start a third counting when the falling edge is detected; the output control units outputs a first enable signal if it is determined that the falling edge that starts the second counter to count is from the first data; the output control units outputs a second enable signal if it is determined that the falling edge that starts the second counter to count is from the second data.
14. The self-adaptive baud rate system according to claim 13 , wherein the output control unit forbids outputs of the first enable signal and the second enable signal, when the third count value from the second counter reaches a third threshold value.
15. The self-adaptive baud rate system according to claim 14 , wherein the first enable signal controls a first transceiver that receives the first data from a first network; and the second enable signal controls a second transceiver that the second data from a second network.
16. The self-adaptive baud rate system according to claim 15 , wherein the first threshold value is a ratio of a different baud rate to the basic clock signal; the second threshold value is a preset value to which a different specific encoding mode corresponds; and the third threshold value is the ratio of a character time corresponding to the baud rate and encoding mode derived by the baud rate detection unit to the basic clock.
17. A Modbus repeater with self-adaptive baud rate, comprising the self-adaptive baud rate system according to claim 9 .
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November 11, 2011
January 6, 2015
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